A study of the effects of selected components in salivary secretions on the first component of complement is proposed. The logic for studying saliva- complement interactions is easily seen when one realizes the whole saliva is composed of not only secretions from the major and minor salivary glands, but also of gingival crevicular fluid which contains a functional complement system(11). The flow rate of gingival crevicular fluid is related to severity of periodontal inflammation (74,75) whereas the flow rate of salivary secretions is under the influence of other types of stimuli (72,73). For example, during sleep, when the flow rate of salivary gland secretions approaches zero (72,73), the gingival crevicular fluid may become a major source of fluid entering the oral cavity of individuals with severe periodontal disease. Thus, the crevicular fluid has the opportunity of coating the surface of the oral cavity which were previously coated with salivary components. We have isolated and partially characterized a group of Ca++ dependent non- immunoglobulin salivary agglutinins from parotid saliva (SBA), which aggregates Streptococcus milleri. From our preliminary studies, we speculate that these isolated SBA activate Cl as determined by Cl fixation tests. We propose in this application to further examine the interactions between SBA and Cl and thereby better understand how saliva effects the function of the complement system in the oral cavity. Specifically, we plan to study in detail the reaction of SBA with Cl and its subcomponents and subsequently, to examine the effects of such interactions on Cl mediated activation of C4 and C2 and subsequent C3 activation. Although SBA have been isolated by several laboratories, completed chemical characterization of these factors is yet to be made. One of our objectives is to chemically characterize these SBA. We also plan to study the effects of SBA on Cl in presence of Cl inhibitor and/or the acidic proline rich salivary proteins, the latter inhibit free Cl but not Cl bound to antibody coated cells. In particular, we wish to determine the effects of these acidic proline rich salivary proteins on Cl function, once Cl is bound to immobilize SBA.